1. Field of the Invention
This invention relates to apparatus for punching holes in sheet material, such as paper.
2. Background of Art
It is common to bind multiple sheets of material, such as paper, using fasteners such as rings, string, metal clasps, etc. Holes are normally pre-punched in the sheet material to accept these fasteners.
One conventional apparatus for pre-punching holes in sheet material is shown at 10 in FIGS. 1-4 herein. The hole punching apparatus 10 consists of a frame 12 defining an upwardly facing, flat support surface 14 for multiple pieces of sheet material 16 into which holes 18 are punched. The frame 12 supports two, tubular, cutting blades 20 for movement relative to the frame 12 between a retracted position, as shown in FIG. 3, and a cutting position, as shown in FIG. 2. The frame 12 has two plastic backing elements 22, provided one each beneath the cutting blades 20. A handle 24 is mounted on the frame 12 and is repositionable from a normal position, shown in FIG. 1, to an actuated position, by pivoting movement of the handle 24 in the direction of the arrow 26 to thereby reposition the cutting blades 20 from the retracted position into the cutting position. In so doing, an annular cutting edge 28, at the free end of each cutting blade 20, is driven through either a single piece of sheet material 16 or through stacked pieces of sheet material 16 to against the plastic backing element 22. The frame 12 supports a guide element 30 with an upturned end 32 which is abuttable to an edge of the sheet material 16 facially abutted to the support surface 14 to predetermine the position of the sheet material 16 relative to the cutting blades 20 for consistent location of the holes 18.
In a typical cutting operation, the piece or pieces of sheet material 16 are placed against the support surface 14 and shifted into a throat portion defined by the frame at 34 and at the same time abutted to the upturned end 32 of the guide element 30. The guide element 30 can be appropriately repositioned by movement in the line of the double-headed arrow 36 to cause the desired hole locations on the sheet material 16 to be aligned precisely beneath the cutting blades 20. The handle 24 is then grasped and pivoted in the direction of the arrow 26, whereupon the cutting edges 28 on the cutting blades 20 engage and penetrate through the sheet material 16 so as to form, in this case, circular cut-outs 38 therefrom. As the cutting edges 28 bear on the backing elements 22, the bottommost piece of sheet material 16 is penetrated fully through by the cutting edges 28.
The cutting blades 20 each have an internal cavity 40 into which the cut-outs 38 are pressed during a punching operation. Each cavity 40 has a cross-sectional area that progressively decreases in diameter moving away from the cutting edge 28 a distance D at which point the cavity 40 has its smallest diameter and area. The diameter of the cavity 40 increases beyond the distance D to a diameter slightly smaller than the diameter of the cut-outs 38 so that the cut-outs 38 become slightly compressed. The snugly held cut-outs 38 are allowed to slide within the cavity upwardly, i.e. in the direction of the arrow 42. As each cutting blade 20 moves from the retracted position into the cutting position, the formed cut-outs 38 become squeezed progressively as they move the distance D from the cutting edge 28 through a neck 44 at the distance D. An annular ledge 46 at the neck 44 abuts to, and thereby resists downward passage of, the cut-outs 38 that have moved to thereabove.
Systems, such as that shown in FIGS. 1-4, may have a number of drawbacks. First of all, a substantial force may be required on the handle 24 to direct the cutting blades 20 fully through a stack of sheet material 16. As the cut-outs 38 accumulate in the cavities 40, the accumulating cut-outs 38 progressively increase the resistance to downward movement of the cutting blades 20.
Another problem that may be encountered is that the cut-outs 38 that do not travel upwardly to beyond the necks 44 tend to spring out when the cutting blades 20 are moved back towards the retracted position. This may result in the cut-outs 38 having to be manually removed from the holes 18 in the sheet material 16 and/or cleaned up in the area surrounding the hole punching apparatus 10.
In order to precisely form the holes 18, and to do so with minimal effort, it is necessary that the cutting edges 28 on the cutting blades 20 remain sharp. In the event that the cutting edges 28 become dull, it is desirable to be able to change the cutting blades 20, rather than replace the entire hole punching apparatus 10. Some hole punching apparatus, similar to that shown at 10 in FIGS. 1-4, do not lend themselves to facilitated replacement of the cutting blades 20.
The invention is directed to a hole punching apparatus having a frame, a blade having a tubular cutting edge and a cavity, and a projection on the frame. The blade is movable relative to the frame between a retracted position and a cutting position. The projection moves into the blade cavity as the blade moves from the retracted position into the cutting position.
With the above construction, the projection can move cut-outs formed in a punching operation sufficiently into the cavity that they do not escape as the blade is moved back into the retracted position.
The hole punching apparatus may further have a drive for rotating the cutting edge around a first axis as the blade moves from the retracted position into the cutting position.
By rotating the cutting edge, cutting of the material in which a hole is to be formed is effected not only by pressure applied in moving the blade towards the cutting position, but also by the rotary movement of the cutting edge. This may reduce the amount of force required to be applied to the blade in moving the blade from the retracted position into the cutting position.
In one form, the cavity has first and second ends spaced along the first axis, with the cutting edge being at the first end of the cavity. The cavity has a diameter taken transversely to the first axis. The diameter of the cavity is non-uniform along the first axis.
In one form, the diameter of the cavity decreases from the cutting edge up to a first predetermined axial distance from the cutting edge towards the second end of the cavity and increases from the first predetermined distance towards the second end of the cavity. The projection extends into the cavity at least the predetermined axial distance from the cutting edge.
The blade may be movable substantially parallel to the first axis between the retracted and cutting positions.
A handle may be provided that is movable relative to the frame between a normal position and an actuated position. The blade is movable from the retracted position into the cutting position as an incident of the handle moving from the normal position into the actuated position.
The handle may be pivotable about an axis as the handle moves between the normal and actuated positions.
The drive may include a drive motor for rotating the cutting edge around a first axis as the blade moves from the retracted position towards the cutting position. A switch may be provided that is placeable selectively in a) an on state to cause activation of the drive motor, and b) an off state to cause deactivation of the drive motor. The switch is moved from the off state into the on state as an incident of the handle moving from the normal position into the actuated position.
The hole punching apparatus may include a blade moving assembly and an adaptor for connecting the blade to the blade moving assembly. The blade moving assembly has a blade holder and a guide case. The blade moving assembly is translatable substantially parallel to the first axis between first and second positions as an incident of which the blade moves from the retracted position into the cutting position, and the blade holder is rotatable relative to the blade moving assembly around the first axis.
The blade may be loosely held by the blade moving assembly so that the blade can be shifted at least transversely to the first axis relative to the blade moving assembly.
The blade moving assembly may be movable from the first position into the second position as an incident of the handle moving from the normal position into the actuated position. The hole punching apparatus may further have a first set of gear teeth which are movable by the handle and a second set of gear teeth on the guide case which cooperate with the first set of gear teeth to cause the blade moving assembly to move from the first position into the second position as an incident of the handle moving from the normal position into the actuated position.
The first set of gear teeth may pivot with the handle about the second axis.
The hole punching apparatus may further include an actuator element which follows pivoting movement of the handle and causes the switch to be changed from the off state into the on state as an incident of the handle moving from the normal position into the actuated position.
A guide bushing may be provided on the frame to guide the blade from the retracted position into the cutting position.
The drive may include a shaft which is rotatable around the first axis, with the shaft being rotatable relative to the guide case around the first axis.
The shaft may be keyed to the blade holder so that the shaft drives the blade holder in rotation around the first axis.
In one form, there is a receptacle for material punched out by the hole punching apparatus on the frame. A passageway is defined through the blade holder and guide case. Material punched out by the hole punching apparatus is capable of communicating through the blade cavity to the passageway and through the passageway to the receptacle for accumulation therein. Provision may be made to empty cut-outs in the receptacle when desired.
In one form, the frame defines a surface to support material on which a hole punching operation is to be performed. The hole punching apparatus may include a pressing assembly which is normally biasably urged away from the support surface. The pressing assembly has a pressing surface which is moved towards the support surface to captively hold material against the support surface as an incident of the blade moving from the retracted position into the cutting position.
The hole punching apparatus may further have a second blade with a second tubular cutting edge and a second cavity. The second blade is movable relative to the frame between a retracted position and a cutting position. A second projection on the frame moves into the second blade cavity as the second blade moves from the retracted position for the second blade into the cutting position for the second blade. The second blade is movable from the retracted position for the second cutting blade into the cutting position for the second blade as an incident of the handle moving from the normal position into the actuated position.
The invention is also directed to a hole punching apparatus having a frame, a blade having a tubular cutting edge and a cavity, and a drive motor. The blade is movable relative to the frame between a retracted position and a cutting position. The drive motor rotates the cutting edge around a first axis as the blade moves from the retracted position into the cutting position.